For generating electrical energy, fuel cells are known which convert chemical reaction energy from a continuously supplied fuel and an oxidant into electrical energy.
Various types of fuel cell are known. The best-known fuel cells are hydrogen and methanol fuel cells. In the direct methanol fuel cell (DMFC), which is distinguished by relatively low heat production, methanol is used as the fuel.
The fuel cell has two electrode plates, which are separated by a semipermeable membrane. One electrode plate forms an anode, whilst the other electrode plate forms a cathode. The anode and cathode are coated with a catalyst. At the anode-side catalyst, methanol is oxidized to form carbon dioxide, and at the cathode-side catalyst, oxygen is absorbed as an oxidant and reduced to form water. In the process, protons are transported through the semipermeable membrane and electrons are passed through a circuit, generating electrical energy.
Using a single fuel cell, only electrical voltages in a range of 1 to 1.2 V can be generated. Therefore, a plurality of individual cells are arranged in a stack. However, in relation to the size of the membrane surface, which is of decisive importance for proton transport and thus for the total power of the fuel cell, this construction is distinguished by relatively large dimensions and a relatively high weight.
DE 199 51 687 A1 discloses a fuel cell comprising a plurality of reaction chambers, which are separated by a polymer electrolyte membrane and in which electrical conductors of differing polarity are alternately arranged. In the fuel cell, the semipermeable membrane is formed from a bundle of membrane hollow fibers, electrical conductors of the same polarity being provided inside and outside the membrane hollow fibers in each case, and in each case being electrically interconnected to form a cathode and an anode.
DE 199 51 687 A1 proposes providing electrical conductors, consisting of thin foils or threads of a conductive material, inside and outside the hollow fiber membranes as the anode and cathode. All of the electrical conductors are interconnected so as to form a joint anode or cathode.